Radio receiving apparatus



Aug" 7, 1928.

A. M. HARDING RADIO RECEIVING APPARATUS Filed Oct. 22, 1926 -4 6 62 10 5% g Viki 033717232 i 4 3/ 56 E J J 2 5 22, 0 .5- 5o if I *26 i0 '1 v I .r 48 1 z 1 1 5:6 av 42; E fl a tili li atonted thug. 7, 1928.

UNITED STATES 1,680,042 PATENT OFFICE.

llJLiBEiEtil? M. HARDING, OF BOSTGN, iMASSACI-IU'SE'ITS, ASSTG-NOR TO FLASH RADIO GOR- IPURA'TION, OF BOSTON, MASSACHUSETTS, A COIt]?ClLEtAEEION OF MASSACHUSETTS.

name nnonivme APPARATUS.

-Application "filetl October 22, 1926.

This invention relates to radio receiving apparatus and particularly to a crystal re ceiving-set.

The primary object of the invention is to provide an eiiicient and compact crystal re ceiving set, preferably of the portable or pocket type, which is extremely simple in construction and highly eilicient in operation, of attractive appearance, and which may be manufactured and assembled at a minimum expense. V

Another object is to provide a crystal receiving set of maximum volume.

l ilith these objectsin view and such others as may hereinafter appear, the preferred form of the invention comprises a crystal receiver enclosed in a flattened casing of dielectric material provided with end memhers of similar material, one or both of which may he removable. i Vithin the casing a tuning coil is carried on a flattened insulating core having a recess within which is mounted a crystal detector, preferably a lined crystal detector, and a choke coil which is arranged at the output end of said crystaldetector so as to influence the radio frequency current afterithas been rectified by the detector.

,To reduce the cost and to simplify theconstruction and enable the apparatus to be connected up in a minimum time, one of the end members of the casing has secured to it outside of the casing a plurality of circuit terminals, preferably Fahnstock clips, to which the telephone and ground wires are connected, and the other end member of the casing has extended through it a slider provided within the casing with a contact 1ncm her which co-operates with the tuning coil and also provided outside of the casing with a circuit terminal with which the antenna is connected.

The particular features of the invention will be pointed out in the claim at the end of this specification.

lln the drawings, which illustrate the preferred form of the invention, Figure 1 is a longitudinal section, partly in elevation, through the improved radio receiver; Fi s. 9; and 3 are end views looking at the left and right ends, respectively, of Fig. 1; and Figs. t and 5 are sectional views taken on the lines H and 5-5, respectively, of Fig. 1.

ln the preferred form the improved radio receiver is enclosed in an elongated casing Serial No. 143,488.

0f fiber or similar material having a high dielectric constant. End members or covers 1.2 and Hot the same or similar material are provided for the casing 10. In order to facilitate handling of the receiving set and provide a relatively flat instrument capable of being carried in the pocket of the user, the casing 10 and end members 12 and 141; are formed in the shape of an oblong having substantially semi-circular side portions, as illustrated in Figs. 2, 3, tand 5.

The casing 10 contains within it an in sulating core 16 of elliptical term having wound thereon the helical tuning coil l8,

which is so proportioned as to permit the receiver to be accurately tuned to all lfrequcncies within the broadcast range.

In the present instance the core 1G is fm'ined ofwood because of the relative cheapness and ease of working this material, but it will readily be understood that other insulating materials, such as hard rubber, fibre, etc. might be used.

The detector used in the improved receiver is preferably in the form of a lined crystal, and in order to aid in producing a compact receiver, the crystal which is indicated at 20 is mounted in a recess or bore 22 formed in the core 16. Gne end or terminal 52 i of the crystal is in electrical contact with the tuning coil 18, which is effected as shown by running the wire 26 of the tuning coil through the core 16 across the bore 22 preferably a plurality of times "(see Figs. 1 and '5).

It has been found. that the sensitivity of the receiver and the intensity of signal strength obtainable therefrom are greatly increased when a choice coil is placed in the secondary circuit at the output end of the crystal detector. The choke coil is made in the form of a coil spring 28 which is located in the recess or bore 22 and electrically connccted with the second terminal or output end 30 of the crystal detector.

The other end of the choke coil 28 is brought out through a hole in the core 16 leading from the bottom of the recess 22 to the opposite end of said core, and is then bent radially outwardly across the end of the core and secured to and in electrical contact with a screw 36 mounted on the end member 12.

The screw 36 also make electrical contact with one end of the telephone terminal 38 members 12 and 14 respectively are screwed into the Opposite ends of the core 16.v

A clip carrying a second telephone terminal 48. and a ground terminal 50' is also secured inposition on the outside of the end member. 12, by the screw 40, and the end 1 52 of the tuning coil 18 is'brought out over the end of the core 16 into electrical contact with" the screw 40, thus connecting this end of the coil,18 to the phone terminal 48 and the ground terminal 50.

. Provision is made for tunin the primary or antenna-ground circuit of t e receiver.

. To this end, a slider bar 54, preferabl square in cross-section, is extended-throng the end member 14 "and through a guidin sp-member 56 secured to the inside of sai end member. I The inner end of the slider bar 54 is screwthreadedat 58 and a spring contact member 60 and a bearing member 62 are secured on saidv screw-threaded end betweenthe nuts 64 and 66. The bearing member 62 is shaped substantially semicircular to fit one, of the rounded side portions of the casing 10, and engages the same to hold the contact member 60 in firm engagement with the coil 18 in all positions of the slider bar v54. v V 7 jgIn order to prevent excessive wear between the'casing 10 and the bearin member 62, the latter is preferably made of relatively hard The end of the slider bar 54 outside of the casing is provided with a screw-threaded portion 68, and an antenna terminal member 270 is'secured thereonbetween nuts 72 and 74. An operating knob .76 of dielectric matector and choke coil located in sai terial is also secured on the screw-threaded end 68 of the slider 54.

The terminals 38, 48, 50 and 70 are preferably Fahnstock clips, and suitable lettering indicated at 78 in Figs. 2 and 3 is formed on the end members 12 and 14 adjacent said terminals to aid in properly connecting up the receiver.

It will be seen from the foregoin description, that a simple, compact, e cient and inexpensive radio receiver has been provided, which may be economically manufactured, and which can be connected in circuit in a minimum time.

By connecting the choke coil with the output end of the crystal detector, the radio frequency is permitted to be rectified by the crystal detector before it is o posed by the choke coil, and as a result, t e volume of the sound at the telephones is increased, thereby obtaining a superior crystal detector receiving set.

While it is referred to use the invention in the form il ustrated and described, it will be understood that it may be embodied in other forms within the scope of the following claim.

What is claimed is:

In a radio receiving set, in combination, a casing provided with end members, a tuning coil within said casing having a core of insulating material rovided with a recess forming a housing or a fixed crystal detector and a choke coil, said fixed cr stal ded housing to be moved with the tuning coil as a unit and with the choke coil connected with the output end of said crystal detector, and a slider provided with a contact member cooperating with said tunin coil. In testimony whereof, T have signed my name to this specification.

ALBERT M. HARDING. 

